The present invention relates to a method and apparatus for separating articles that are supplied in bulk and sorting the articles in accordance with their weight. The invention is especially useful for sorting food products such as shrimp, vegetables, fruits and the like which are typically supplied in large bulk containers of mixed sizes and weights and are then subdivided into smaller quantities for sale to the consumer.
Products such as shrimp, apples, potatoes and other food products when harvested do not have a uniform size and weight, but frequently are sold the consumer in packages in which the articles are generally uniform in size and weight. In other instances articles are sold with an intended homogeneous mixture of sizes. In both cases, the uniformity of size or the homogeneity of the mixture cannot be guaranteed by simply withdrawing the articles randomly from a bulk supply. Instead, the articles must be taken from the bulk supply and classified by size or weight, and then be reassembled in individual packages according to the size or mixture standards desired.
The necessity for classifying articles extends beyond the desires of the consumer, and in may cases is imposed by the physical constraints of the packaging processes or machines. For example, a pound of medium shrimp may contain as many as 27 shrimp or as few as 18 shrimp. If the packages in which the shrimp are sold are guaranteed to have a given piece count, and all of the shrimp delivered to a particular package are larger than normal, an average size package may not be large enough to enclose all of the shrimp or sealing of the package may at least be made difficult. Providing extra large packages to accommodate the occasional group of large shrimp is commercially unacceptable because the average package will then appear to be only partially filled.
Sometimes articles may be sold by both piece count and weight in which event the bulk quantities of shrimp must also be subdivided and classified according to weight prior to packaging. In this manner the consumer is assured of a relatively uniform size of product in the package, and the packages themselves may be sized to accommodate the intended piece count without appearing to be over- or underfilled.
The process of separating and sorting articles according to weight is not new and is described in several prior U.S. patents. U.S. Pat. No. 4,413,739 describes an automatic weight sorter which uses a belt conveyor and dynamic weighing device integrated with the conveyor for sorting articles that have already been placed individually on the conveyor. The patent does not reveal how the articles arrive at the conveyor, and the box-shaped representation of the articles suggests that the articles are packages that are manually loaded on the conveyor.
U.S. Pat. No. 4,818,380 discloses a sorting apparatus utilizing a conveyor and an image analysis system for classifying the articles by size. The apparatus is useful for sorting fruits and vegetables but again there is no indication of how the fruits and vegetables are loaded onto the conveyor so that each article can be examined individually for a size determination.
U.S. Pat. No. 4,096,590 discloses a sorting system that utilizes an overhead conveyor and an integrated weigh station for sorting individual poultry carcasses according to weight. The carcasses are loaded onto the overhead conveyor by a releasable clamp which suggests that the articles are separated from any bulk supply of the carcasses by hand.
While each of the prior art apparatuses discussed above sorts articles according to size or weight, none of them is suitable for separating the articles from bulk supplies to perform the disclosed sorting functions. Furthermore, dynamic scales integrated with a conveyor are not suitable for sorting and accurately classifying small, light weight articles such as shrimp.
It is accordingly a general object of the present invention to disclose a separating and sorting apparatus that is especially useful for articles that are supplied in bulk.